Boat propulsion device

ABSTRACT

A propelling machine ( 2 ) is configured curved- tubular, on a ship bottom ( 1 b), with a front casing ( 12 ) having a suction inlet ( 11 ) opening fore to water, an impeller casing ( 10 ) having an impeller ( 17 ) inscribed thereto, and a rear casing ( 14 ) having a delivery outlet ( 13 ) opening aft to water, and the impeller ( 17 ) is forward and reverse rotatable.

TECHNICAL FIELD

[0001] This invention relates to a propulsion system for boats such as aboat to run a shallow, for example, a carrier or a houseboat, or a craftequipped with an auxiliary propulsion system, for example a yacht.

BACKGROUND ART

[0002] Japanese Patent Application Laying-Open Publication No.Hei-6-219389 has disclosed a propulsion system for a wind-poweredsailing boat that employs, upon entry into or departure from a port orwhen in a calm, an auxiliary propulsion system having a propellerprojecting from the bottom of the boat. Japanese Patent ApplicationLaying-Open Publication No. Hei-6-107280 has disclosed a boat propulsionsystem of a counter-rotating double-propeller type in which swirlingstreams generated by a fore propeller are rectified into straightstreams by an aft propeller.

[0003] Propulsion systems for boats to be propelled by a propeller andsteered with a helm to change the direction of course like above areallowed to be relatively simple in arrangement for acquisition of apropelling force to be great, and adapted for transportation of heavymaterials, subject to the provision of a shaft projecting from thebottom of boat in the water for mounting the propeller, which has thefollowing problems:

[0004] (1) The propeller may bite sands or rock in a shallow, or havestring-like drifting matters bound thereon, with a damage to thepropeller or the shaft.

[0005] (2) In the case of a yacht, the propeller shaft may act as afluid resistance to the water, constituting a hindrance to the travelspeed. A drive for the propeller may have noisy rotation sounds, as ithas a clutch disengaged when sailing.

[0006] (3) The boat needs to be brought onto the shore for repair orreplacement of the propeller.

[0007] To this point, Japanese Utility Model Application Laying-Openpublication No. Hei-6-61695 has disclosed a propulsion system for boats,which has a swirling vortical casing incorporated in a hull, with asuction inlet and a delivery outlet confronting the bottom, and in whichwater is drawn by suction at from the suction inlet, to an impellerinstalled thereabove, where it is pressurized and converted intoswirling streams, which are discharged as jets from the delivery outletto produce a propelling force, while the vortical casing is rotatableabout a vertical axis to change the direction of course, withadvantageous adaptation for travel such as on a shallow.

[0008] Propulsion systems for boats with arrangement like above areadapted, without projections from the bottom, for travel on a shallow,and with provision of the vortical casing turnable to effect backwardand transverse travels, for approach to and departure from a pier,subject to the following problems:

[0009] (4) Pressurized swirling streams fill the casing, to bedischarged as jets, needing a conversion from kinetic energy of theimpeller to energy for pressurizing streams to be swirled and aconversion from the pressurizing energy to kinetic energy of jets to bedischarged, with losses of energy decreasing efficiency.

[0010] (5) The area effective for horizontal jet discharge is kept frombeing increased in comparison with the casing size, with a lowpropulsion efficiency in the horizontal direction.

[0011] (6) Upon switch between forward and backward travels, an entiretyof the casing integrated with the delivery outlet is turned to changethe direction, which is heavy, and needs the system to be full-scaled.

DISCLOSURE OF THE INVENTION

[0012] This invention has been made with the above-noted problems inview, and it is an object to be solved by the invention, to provide apropulsion system for boats with an incorporated impeller capable ofswitch between forward and backward travels without turning an impellercasing.

[0013] According to an aspect of the invention, in a propulsion systemfor boats, a propelling machine is configured curved-tubular, on abottom of boat, with a front casing having a suction inlet opening foreto water, an impeller casing having an impeller inscribed thereto, and arear casing having a delivery outlet opening aft to water, and theimpeller inscribed to the impeller casing is forward and reverserotatable, whereby water drawn by suction from the front casing andpressurized water to be discharged as jets from the rear casing arechangeable in water stream directions inside the propelling machine, asthe impeller is rotated forward or reverse, allowing for the boat tohave a switched travel direction between forward travel and backwardtravel, with a great propelling force obtainable by discharging jets ofpressurized water into the water.

[0014] The impeller inscribed to the impeller casing may preferably beconfigured as a counter-rotating double impeller comprising a frontimpeller and a rear impeller, whereby a greater propelling force than bya single impeller is obtainable with an improved suction performance dueto water streams in travel and an improved delivery performance due tocounter rotation of double impellers.

[0015] The impeller inscribed to the impeller casing may preferablycomprise axial flow blades, whereby extended blade surfaces can exertincreased pressurizing forces on water in forward and reverse rotations.

[0016] In particular, as the counter-rotating double impeller has axialflow blades, swirling streams of water pressurized at the front impellercan be guided onto blade surfaces of the rear casing, with increasedpush-in pressures, to be converted into straight streams by the rearimpeller, where they are additionally pressurized.

[0017] The impeller casing and the front casing and the rear casingconnected to front and rear ends of the impeller casing may preferablyhave flow paths thereof substantially identical in size of insidediameter, whereby discharge power of pressurized water can besubstantially equalized between forward rotation and reverse rotation,allowing for the boat to have a propelling force of forward travel, evenin backward travel.

[0018] The impeller casing may preferably be configured arcuate, and adrive shaft with the impeller fixed thereon may preferably be supportedby bearings disposed on front and rear peripheral walls of the impellercasing, whereby the drive shaft with the impeller fixed thereon can beevenly supported, with reduced vibrations.

[0019] The impeller casing may preferably be configured cylindrical, anda drive shaft with axial flow blades fixed thereon may preferably besupported by a bearing support connected to a rear end of the impellercasing and a bearing on a side wall of the front casing, wherebyvibrations can be reduced, allowing the propelling machine to becompact, as well.

[0020] The suction inlet of the front casing and the delivery outlet ofthe rear casing may preferably have plural rectification vanes,respectively, whereby water streams drawn by suction are guided into thefront casing, and swirling water streams are rectified to be discharged,with an improved propelling performance, while preventing foreignmatters from in flowing. If rectification vanes of the front casing areblocked with foreign matters, the impeller can be reverse rotated towash off the foreign matters blocking the rectification vanes.

[0021] The front casing may preferably have a suction flow path inclinedfore, and the rear casing may preferably have a delivery flow pathinclined aft, whereby suction of water streams in travel as well as aftdischarge of jets into the water can be performed with an increasedpropelling force, allowing an application to a large-scale boat such asa carrier or yacht.

[0022] The front casing and the rear casing of the propelling machinemay preferably be connected or fastened at lower ends thereof to fixingflanges, and the fixing flanges may preferably be detachably attached toopenings of the bottom of boat, whereby the structure can be compactwithout projections at the bottom of boat, with possible noisereduction. The propelling machine can be configured as a unit attachableto and detachable from the boat bottom.

[0023] The impeller casing may preferably be separable fore and aft,whereby the impeller casing with the inscribed impeller can be assembledor disassembled with ease, facilitating the cleaning inside the impellercasing, as well as removal of rope or string-like matters binding on theimpeller.

[0024] The impeller casing may preferably be separable into an upperhalf of impeller casing and a rear half of impeller casing, and thedrive shaft may preferably be supported by the upper half of impellercasing, whereby the upper half of impeller casing supporting the shaftof the impeller can be removed from the propelling machine, facilitatingmaintenance services such as repairing.

[0025] An inspection hole may preferably be provided to the impellercasing in a vicinity of the impeller, whereby the impeller casing can beinternally inspected with ease, with possible prevention of damages thatotherwise might occur to the impeller or the like.

[0026] A boat-side fronting branch path may preferably be branched fromthe rear casing, to be cooperative with the rear casing to effect a flowpath selection therebetween, whereby transverse propulsion can beachieved.

BRIEF DESCRIPTION OF THE DRAWINGS

[0027]FIG. 1 is an elevation of a yacht equipped with a propulsionsystem according to an embodiment of the invention;

[0028]FIG. 2 is a partially longitudinally cutaway side view of thepropulsion system of FIG. 1;

[0029]FIG. 3 is a longitudinal sectional view of a propelling machine ofthe propulsion system of FIG. 2;

[0030]FIG. 4 is an exploded longitudinal sectional view of an impellercasing of the propelling machine of FIG. 3;

[0031]FIG. 5 is a bottom view of the propulsion system of FIG. 3;

[0032]FIG. 6 is an illustration of a forward-reverse rotation shifter ofthe propulsion system of FIG. 3;

[0033]FIG. 7 is a longitudinal sectional view of a propulsion system forboats according to another embodiment of the invention;

[0034]FIG. 8 is an illustration of a counter-rotating double impeller ofthe propulsion system of FIG. 7;

[0035]FIG. 9 is a perspective view of a propulsion system for boatsaccording to another embodiment of the invention;

[0036]FIG. 10 is a longitudinal sectional view of a propulsion systemfor boats according to another embodiment of the invention;

[0037]FIG. 11A to FIG. 11D show a propulsion system for boats accordingto another embodiment of the invention, in which FIG. 11A is a plan ofthe propulsion system, FIG. 11B is a side view of the propulsion system,FIG. 11C is a section of arrow-indicated portion XIC of FIG. 11B, andFIG. 11D illustrates a flow path selection mechanism of the propulsionsystem; and

[0038]FIG. 12 is a hydraulic circuit for forward-reverse rotationshifter.

PREFERRED EMBODIMENTS OF THE INVENTION

[0039] There will be detailed below preferred embodiments of theinvention, with reference to the accompanying drawings. Like members orelements are designated by like reference characters.

[0040]FIG. 1 shows a yacht Y equipped with an auxiliary propulsionsystem Ap according to a first embodiment of the invention, FIG. 2 andFIG. 5 show the auxiliary propulsion system Ap, and FIG. 3 and FIG. 4show a propelling machine 2 of the auxiliary propulsion system Ap.

[0041] The yacht Y is built with a hull 1 equipped with a single mast 1m and a set of sails 5 as a principal propulsion system. The hull 1 isequipped, at a bottom 1 b thereof, with a keel 6 disposed aft (on a bow1 c side) of the mast 1 m, and a helm 4 projecting beneath a stern 1 a,and has the auxiliary propulsion system Ap incorporated therein betweenthe mast 1 m and the helm 4 and fixed on an upside of the bottom 1 b

[0042] The auxiliary propulsion system Ap is made up by a water jetpropelling machine 2, an internal combustion engine 3 for driving thepropelling machine 2, and a forward-reverse rotation shifter 8 installedbetween the internal combustion engine 3 and the propelling machine 2.

[0043] The propelling machine 2 is configured with a drive shaft 9coupled for connection to the forward-reverse rotation shifter 8, amulti spiral-blade impeller 17 keyed to the drive shaft 9, a impellercasing 10 as a water flow path circumscribed to the impeller 17 with aminute clearance, and a front casing 12 and a rear casing 14 connectedto front and rear ends of the impeller casing 10, respectively, andarranged to open through the bottom 1 b.

[0044] In the auxiliary propulsion system Ap, the internal combustionengine 3 drives the propelling machine 2, whereby water is drawn bysuction from a fore (or aft) water region and discharged as jets ofpressurized water into an aft (or fore) water region, giving apropelling force for the yacht Y to travel or run forward (or backward).The course of yacht Y can be changed by the helm 4.

[0045] The yacht Y is propelled to travel with the propelling machine 2driven by the internal combustion engine 3, in entry to or departurefrom a port or when in a calm, or with the set of sails 5 receivingwinds, in a race or offshore travel, and steered by the helm 4. Thispropulsion system Ap is applicable also to a carrier or houseboat fortravel on a shallow.

[0046] The forward-reverse rotation shifter 8 is connected between anoutput shaft 7 of the internal combustion engine 3 and the drive shaft 9of the propelling machine 2.

[0047] As shown in FIG. 3, the propelling machine 2 is configuredcurved-tubular as a combination of the impeller casing 10, which isarranged horizontal above the bottom 1 b at the stern 1 a, and formedcylindrical at an intermediate part and curved at both ends, to beshaped arcuate, the front casing 12, which is connected to one end ofthe impeller casing 10 and has a suction inlet 11 opening to the waterat the bottom 1 b on the fore side, and the rear casing 14, which isconnected to the other end of the impeller casing 10 and has a deliveryoutlet 13 opening to the water at the bottom 1 b on the aft side.

[0048] The impeller casing 10 has curved peripheral walls, wherebearings 15 and 16 are disposed, which bearings 15 and 16 of theimpeller casing 10 serve for horizontally supporting the drive shaft 9with the impeller 17 fixed thereon.

[0049] The impeller 17 thus disposed in the impeller casing 10 is forcedto rotate forward or reverse, by the internal combustion engine 3 ofwhich output is shifted at the forward-reverse rotation shifter 8. Theimpeller 17 is evenly supported in the intermediate part of the impellercasing 10, with reduced vibrations.

[0050] The impeller casing 10 is connected, as shown in FIG. 3, at theintermediate part by flanges 18, 18, where it is separable fore and aft,as shown in FIG. 4. The impeller casing 10 has at both ends thereofflanges 19 and 20 formed thereon to be fastened to flanges 19 and 20formed at upper ends of the front casing 12 and the rear casing 14,respectively, whereby assembly as well as disassembly of the propellingmachine 2 is facilitated.

[0051] As shown in FIG. 3, the suction inlet 11 of the front casing 12is provided with a plurality of rectification vanes 21 arrayed thereinand inclined with their lower ends positioned fore, for guiding, intravel, streams of water to inflow the suction inlet 11 of the frontcasing 12, with increased push-in pressures. The rectification vanes 21are arranged parallel, with a screening function to prevent foreignmatters from entering the front casing 12.

[0052] The delivery outlet 13 of the rear casing 14 also has a pluralityof rectification vanes 22 arrayed therein and inclined with their lowerends positioned aft, for rectifying swirling streams of waterpressurized by he impeller 17 into straight streams to be discharged asrearward jets in a water region on the aft side at the stern 1 b, givinga propelling force for the boat 1 to travel forward.

[0053] As shown in FIG. 3 and FIG. 5, the front casing 12 as well as therear casing 14 has at the lower end a rectangular fixing flange 23fitted thereon, which fixing flange 23 is detachably attached to befixed to the bottom 1 b. The propelling machine 2 is thus united in acompact structure, wherein noises are reduced and whereby the fixing aswell as removal of the propelling machine 2 to and from the hull 1 isfacilitated.

[0054]FIG. 6 shows the forward-reverse rotation shifter 8 installedbetween the internal combustion engine 3 and the impeller 17. The gearcase rotatably supports an input shaft 24 and an idle shaft 25, whichare coupled or operatively connected with the output shaft 7 of theinternal combustion engine 3. A first gear 27 fixed on the input shaft24 and a second gear 26 fixed on the idle shaft 25 mesh with each other,rotating in opposite directions.

[0055] The input shaft 24 and the idle 25 have at their distal ends afirst transmission gear 29 and a second transmission gear 30 fixedthereon, respectively, which first and second transmission gears 29 and30 mesh with a drive gear 31 fixed on the drive shaft 9, which isinserted into the gear case. A forward-propulsion oriented multi-discclutch 32 is fitted to the input shaft 24, whereto the firsttransmission gear 29 loose-splined on the shaft is hydraulicallyoperatively connected to effect forward rotation of the impeller 17 onthe drive shaft 9.

[0056] A backward-propulsion oriented multi-disc clutch 33 is fitted tothe idle shaft 24 as well, whereto the second transmission gear 30loose-splined on the shaft is hydraulically operatively connected toeffect reverse rotation of the impeller 17 on the drive shaft 9.

[0057] As shown in FIG. 3, the inside diameter of the impeller casing 10and those of the front casing 12 and the rear casing 14 aresubstantially identical in size, so that discharge power of pressurizedwater jets is substantially equalized between forward and reverserotations of the impeller 17, allowing for the hull 1, even in backwardtravel, to obtain the propelling force of forward travel, effecting afast switching between forward travel and backward travel of the boat.

[0058] As an output of the internal combustion engine 3 has a rotationaldirection switched reverse by the forward-reverse rotation shifter 8,water incoming from the delivery outlet 13 of the rear casing 9 at thebottom 1 b is guided by the rectification vanes 22, to be transmitted toan aft end of the impeller 18. Water transmitted to the rear side of theimpeller 18 is pressurized by the impeller 18 in reverse rotation, andresultant swirling streams of water are rectified by the rectificationvanes 21 disposed at the suction inlet 11 of the front casing 12, to bedischarged fore as water jets, of which a propelling force propels thehull 1 to travel backward. In the backward travel, a turning can also bepossible by the helm 4.

[0059]FIG. 7 shows a propulsion system Pr1 for boats according toanother embodiment of the invention. This propulsion system Pr1 has apropelling machine 2 a provided with a counter-rotating double impeller34 in an impeller casing 10 a, which is configured as a combination of afront impeller 34 a and a rear impeller 34 b fixed on a hollow driveshaft 35 and a drive shaft 36, respectively, with the drive shaft 36coaxially inserted in the hollow drive shaft 35. The hollow drive shaft35, on which the front impeller 34 a is fixed, and the drive shaft 36,on which the rear impeller 34 b is fixed, are operatively connected to aforward-reverse rotation effecter 37.

[0060] In the embodiment Pr1 shown in FIG. 7, a front casing 12 a of thepropelling machine 2 a has a suction flow path A inclined fore, and arear casing 14 a has a delivery flow path B inclined aft, so that alower end of the front casing 12 a is substantially parallel torectification vanes 21 arranged in a suction inlet 11 a, providingstreams of water during travel with increased tendencies to enter thefront casing 12 a from the suction inlet 11 a.

[0061] A delivery outlet 13 a at a lower end of the rear casing 14 a issubstantially parallel to rectification vanes 22, so that streams ofwater guided by the rectification vanes 22 of the rear casing 14 a aredischarged aft as jets into the water under the boat bottom 1 b.Designated by reference character 23 a is a fixing flange fastened tothe lower end of the front casing 12 a, as well as of the rear casing 14a.

[0062] As shown in FIG. 8, the forward-reverse rotation effecter 37 isconfigured to be accommodated in a gear case 41, with a sun gear 38fixed on a proximal end of a drive shaft 36, a plurality of planet gears39 arranged about the sun gear 38, meshing therewith, and an internaltoothed gear 40 as a ring gear fixed on a proximal end of a hollow driveshaft 35 and engaged for meshing with outer peripheries of the planetgears 39, so that, as the sun gear 38 rotates, the internal gear 40 isreverse-rotated via the planet gears 39, thereby rotating in oppositedirections the hollow drive shaft 35, on which the front impeller 34 ais fixed, and the drive shaft 36, on which the rear impeller 34 b isfixed.

[0063] In the propelling machine 2 a provided with the reverse-rotatingdouble impeller 34, inflowing water from the suction inlet 11 a of thefront casing 12 a is pressurized and converted into swirling streams bythe front impeller 34 a, which are guided onto blade surfaces of therear impeller 34 b, which converts them into straight streams, exertingthereon increased push-in pressures, effecting additionalpressurization. Rotational power is energy-converted into pressures atthe counter-rotating double-impeller 34, and high-pressure jets aredischarged into the water from the delivery outlet 13 a of the rearcasing 14 a, whereby the boat is propelled forward, while the course ofboat is turnable by a helm.

[0064] The propelling machine 2 a provided with the reverse-rotatingdouble impeller 34 has an increased propelling force, and is adapted, asthe propelling machine 2 a has no projections under the boat bottom 1 b,for such applications as to a houseboat with a shallow draft and ashallow travelling boat.

[0065] It is noted that the propelling machine 2 shown in FIG. 3 may aswell be modified to have a counter-rotating double impeller 34 in placeof the single stage impeller 17.

[0066] The forward-reverse rotation effecter 37 coupled for connecttionto the propelling machine 2 a as shown in FIG. 7 is connected to theforward-reverse rotation shifter 8 direct-coupled with the internalcombiustion engine 3 as shown in FIG. 6, so that rotation of the outputshaft 7 of the internal combustion engine 3 is transmitted via theforward-reverse rotation shifter 8, where the rotation is shifted fromforward to reverse, thereby switching, into mutually opposite rotatoinaldirectoins, the front impeller 34 a and the rear impeller 34 b of thecounter-rotating double impeller 34 that the forward-reverse rotationeffecter 37 operates.

[0067] As an output of the internal combustion engine 3 is transmittedvia the forward-reverse rotation shifter 8 set to shift the rotationinto a reverse direction for reverse-rotating the counter-rotatingdouble impeller 34, the rear casing 14 a draws water by suction from thedelivery outlet 13 a submerged under the boat bottom 1 b at the stern 1a, and water transferred to the rear side of the rear impeller 34 b ispressurized and converted into swirling streams by the rear impeller 34b, which are rectified by the front impeller 34 a, to be discharged foreat the suction inlet 11 a of the front casing 12, as jets of pressurizedwater into the water, whereby the boat is propelled backward.

[0068] If foreign matters are caught on the rectification vanes 21 atthe suction inlet 11 a of the front casing 12 a, blocking the suctioninlet 11 a, then the counter-rotating double-impeller 34 can bereverse-rotated for discharging pressurized water streams from insidethe front casing 12 a to wash off the foreign matters blocking thesuction inlet 11 a.

[0069] In the embodiment Pr1 shown in FIG. 7, a impeller casing 10 a isconfigured with an inspection hole 42 to enable an inspection into theimpeller casing 10 a, where the counter-rotating double impeller 34 isdisposed.

[0070]FIG. 9 shows a propulsion system Pr2 for boats according toanother embodiment of the invention. This propulsion system Pr2 includesa propelling machine 2 b configured with: an impeller casing 43, whichis divided into an upper casing 43 a as an upper half thereof and alower casing 43 b as a lower half thereof, which are joined together byflanges 44, 44; and a drive shaft 9 a supported by bearings 15 a and 16a arranged on a peripheral wall of the upper casing 43 a.

[0071] The lower casing 43 b is integrally formed with a front casing 45and a rear casing 46 disposed fore and aft, the front casing 45 and therear casing 46 being each connected at lower end thereof to a fixingflange 47. The upper casing 43 a is removable for an overhal orreplacement of an impeller 17 or counter-rotating double impeller 34 tobe facilitated, as well as for removal of string-like matters bindingthereon.

[0072] It is noted that the inspection hole 42 of the impeller casing 10a of FIG. 7 may preferably be provided to either part of the impellercasing 10 divided fore and aft as shown in FIG. 3, or to the uppercasing 43 a of the impeller casing 43 divided up and down as shown inFIG. 9.

[0073]FIG. 10 shows a propulsion system Pr3 for boats according toanother embodiment of the invention, in which a propelling machine 48has a front casing 51 defining a suction flow path A′ inclined fore, anda rear casing 53 defining a delivery flow path B′ inclined aft.

[0074] The front casing 51 has a suction inlet 50, where a plurality ofrectification vanes 58 . . . are arranged with their lower endsmoderately slanting fore in a curvilinerar form for guiding streams ofrunning water inflowing the suction inlet 50 of the front casing 51, tothereby increase push-in pressures to the impeller casing 49, havingenhanced water pressurizing forces along connected blade surfaces ofaxial flow blades 55.

[0075] The rear casing 53 has a delivery outlet 52, where also aplurality of rectification vanes 59 . . . are arranged with their lowerends moderately slanting aft in a curvilinerar form for convertingswirling streams of water pressurized by the axial flow blades 55 intostraight streams, discharging as jets into the water under the stern 1b, with a propelling force to propel the boat forward.

[0076] The front casing 51 as well as the rear casing 53 is connected atthe lower end to a fixing flange 96, so that the propelling machine 48is detachably attached as a unit to the boat bottom 1 b.

[0077] The impeller 17 or 34 inscribed to the impeller casing 10 asshown in FIG. 3 may also preferably be cofigured with axial flow bladesfor having water pressurizing forces substantially equalized betweenforward and reverse rotations, with a sufficient increase in waterpressurizing force when the axial flow blades are reverse rotated. Inparticular, in arrangement of the propelling machine 2 a shown in FIG.7, as the counter-rotating double impeller 34 inscribed to the impellercasing 10 a is configured with axial flow blades, swirling streams ofwater pressurized by the front impeller 34 a can be guided onto bladesurfaces of the rear impeller 34 b with increased push-in pressures, sothat the rear impeller 34 b can additionally pressurize drawn water,while effecting conversion into straight streams.

[0078]FIG. 11A to FIG. 11D show a propulsion system Pr4 for a yacht Yaccording to another embodiment of the invention, in which FIG. 11A is aplan of the propulsion system Pr4, FIG. 11B is a side view of thepropulsion system Pr4, FIG. 11C is a section of arrow-indicated portionXIC of FIG. 11B, and FIG. 11D illustrates a flow path selectionmechanism of the propulsion system Pr4.

[0079] The propulsion system Pr4 is configured with a U-shaped impellercasing 62 analogous in arrangement to the impelling machine 2, a set ofa front casing 66 and a 3-way casing 61 connected vy flanges 76 and 75to front and rear ends of the casing 62, respectively, and a set of arear casing 63, a left casing 64, and a right casing 65 connected byflanges 72, 73, and 74 to the 3-way casing 61 and substantiallyhorizontally opening to the water at a stern 1 c, a left side, and aright side of the yacht, respectively. The rear casing 63, left casing64, and right casing 65 are fixed to a hull 1 at delivery outletsthereof, where respective pluralities of horizontal rectification platesare arranged. The front casing is aanalogous in arrangement at thedelivery end to the propelling machine 2. For driving a single stageimpeller 68 or a counter-rotating double impeller 68+79, there isprovided a drive shaft 67, which also has analogous arrangement inconnection with an internal combustion engine to the case of auxiliarypropulsion system Ap. It is noted that, as illustrated in FIG. 11A, theimpeller casing 62 may preferably be joined at an intermediate partthereof by a flange 71 for convenient inspection or maintenance.

[0080] As shwon in FIG. 11C, the 3-way casing 61 has a flow pathselection valve 80 incorporated therein for selecting an arbitrary oneof leftward, rearward, and rightward flow paths to thereby propel theyacht Y rightward, forward, or leftward.

[0081] The arrangement of the embodiment Pr4 may preferably be appliedto any embodiment else.

[0082]FIG. 12 show a hydraulic circuit for forward-reverse shifter orclutch applicable to each embodiment described.

[0083] In this hydraulic circuit, as a switching valve 90 is operated bya switching lever 90 a, the hydraulic pressure is switched between aforward propulsion clutch 91 and a backward propulsion clutch 92, whichare connected to an associated operational part of a forward-backwardpropulsion switching mechanism. In the figure, designated by referencecharacter 93 is a pressure control valve, 94 is a hydraulic pump, and 95is an oil tank.

[0084] As will be seen from the foregoing description, in a propulsionsystem for boats according to the invention, as an impeller provided inan impeller casing is driven for rotation by an internal combusitonengine, water is guided from a suction inlet at a boat bottom, alongrectification vanes, to be drawn by suction into a front casing, whileentry of foreign matters such as dust is prevented by the rectificationvanes provided plural in the suction inlet of the front casing.

[0085] Then, water inflows the inpeller casing, where it is pressurizedby the impeller, and swirling streams of pressurized water are convertedinto straight streams by rectification vanes of a rear casing, so thatswirling power is energy converted into pressures, whereby jets ofpressurized water are discharged aft into the water from a deliveryoutlet at the boat bottom, propelling the boat forward.

[0086] If the rectification vanes of the front casing are blocked withforeign matters, the impeller can be reverse rotated, so that waterdrawn by suction from the delivery outlet of the rear casing isdischarged as pressurized water jets from the suction inlet of the frontcasing, washing off the foreign matters blocking the rectificationvanes.

[0087] The impeller to be prodived in the impeller casing of thepropelling machine may prefearbly comprise a counter-rotatingdouble-impeller, with an improved suction performance due to waterstreams during travel, and an improved delivery performance due tocounter rotation of double impellers, with a greater propelling forcethan by a single impeller.

[0088] The impeller to be inscribed to the impeller casing maypreferably comprise axial flow blades, having substantially equalizedwater pressurizing forces, whether forward rotation or reverse rotation,with a sufficient increase in pressurizing force to water due to reverserotating axial flow blades.

[0089] In particular, the counter-rotating double impeller maypreferably comprise axial flow blades, so that swirling streams of waterpressurized by a front impeller are guided onto blade surfaces of a rearimpeller, with increased push-in pressures, and converted into straightstreams, with additional pressurization, achieving an increasedcollection efficiency by conversion of rotation energy into pressureenergy.

[0090] To propel the boat backward, the impeller is rotated reverse, sothat water drawn by suction from the delivery outlet of the deliverycasing is discharged as jets from the front casing, for backwardpropulsion, with an amount of pressurized swirling water substantiallyequalized in the reverse rotation to that in a forard rotation of theimpeller of axial flow blades, allowing haste switch between forwardtravel and backward travel. For a large-scale vessel with a plurality ofpropelling machines disposed at the stern, an impeller at the turningside may be reverse rotated for cooperation with a helm to have a smallturning range. For ispection or maintenance of propelling machine, theimpeller casing may be removed, allowing a facilitated overhall orinternal cleaning of an impeller installed therein.

[0091] A small-scale boat may be lifted above the water surface,allowing a repair of the propelling machine or replacement ofconsumables on the sea.

[0092] The rear casing may be branched to have branch flow paths facingboat sides, for cooperation with the rear casing to enable a flow pathselection therebetween, allowing tranverse propulsion.

[0093] Therefore, according to the invention, there is achieved anarrangement in which the direction of water suction by a propellingmachine as well as the discharge direction of pressurized water jets canbe switched for a boat to travel forward or backward, with a minimizedenergy loss for reversing rotatoin of water streams, thus providing anincrased propelling force, with a facilitated maintenance.

[0094] In other words, a boat or yacht equipped with an impeller in thepast might have suffered in a shallow, from possible damages to theimpeller or an inpeller shaft due to a hitting such as to sands. In apropulsion system having a vortical casing equipped inside a boatbottom, with a vertical axis,kinetic energy to be given to water by animpeller is once converted into pressure energy before re-conversioninto kinetic energy, with a great loss in the energy conversion,contrary to the invention in which, without such conversion, a frontcasing of which a suction inlet is open in a fore water region and arear casing of which a delivery outlet is open in an aft water regionare connected to an impeller casing of which an impeller is rotatableboth forward and reverse, with an increased propelling force andpossible haste switch between forward travel and backward travel ofboat.

[0095] An impeller inscribed to an impeller casing may preferably beconfigured as a counter-rotating double impeller, with a front impellergiving an increased push-in pressure and a rear impeller for convertingswirling streams ionto straight streams with additional pressurization,allowing for the conversion from energy of rotational streams topressure energy, with a greater propelling force than a single impeller.

[0096] The impeller to be inscribed to the impeller casing maypreferably configured with axial flow blades, having equalized amountsof swirling pressurized water in forward rotation and reverse rotation,achieving in backward travel of boat the propelling force of forwardtravel.

[0097] The propelling machine may preferably have flow paths thereofsubstantially identical in size of inside diameter to achievesubstantially equalized discharge forces of pressurized water, whetherthe impeller is rotated forward or reverse.

[0098] The impeller casing may preferably be configured with arcuatefront and rear peripheral walls for supporting a drive shaft of theimpeller to be rotated with reduced vibrations and a shortened shaftlength.

[0099] A bearing support of the impeller casing formed cylindrical and abearing on a side wall of the front casing may preferably support adrive shaft on which axial flow blades are fixed, allowing the shaftlength to be short, as well as the propelling machine to be compact.

[0100] In the propelling machine, the suction inlet of the front casingas well as the delivery outlet of the rear casing may prefearbly have aplurality of recitification vanes arranged therein for guiding waterstreams under suction and rectifying pressurized swirling streams toimprove propsulsion efficiency, besides possible removal of foreignmatters.

[0101] The front casing may preferably have a suction flow path inclinedfore and the rear casing may preferably have a delivery flow pathinclined aft, allowing suction of runing water streams during travel andaft discharge of jets in the water to provide an incerased propellingforce.

[0102] The font casing as well as the rear casing may preferably befastened at the lower end to a fixing flange, achieving a compactarrangement without projections at the bottom of boat, allowing for thepropelling machine to be attached to or detached from the bottom, as aunit, with ease, so that an inspection or repair thereto can beperformed on the sea by lifting the boat.

[0103] The impeller casing may preferably be configured separable,allowing for facilitaetd assembly and disassembly of the impeller casingto which the impeller is inscribed, facilitating an overhall of theimpeller disposed inside the impeller casing, as well as an internalcleaning of the propelling machine.

[0104] An inspection hole may preferably be provided to the impellercasing in a vicinity of the impeller, with a facilitated inspection intothe impeller casing, allowing damages such as to the impeller to beprevented in advance.

[0105] The rear casing may preferably be branched to provide a branchpath facing a boat side, for cooperation with the rear casing to enablea flow path selection therebetween, enabling a transverse propulsion.

INDUSTRIAL APPLICABILITY

[0106] According the invention, there is provided a propulsion systemfor boats with an incorporated impeller, allowing switch between forwardand backward travels without turning the impeller, with simplified boatequipment.

1. A propulsion system for boats, wherein: a propelling machine (2, 2 a,2 b, 48) is configured curved-tubular, on a ship bottom (1 b), with afront casing (12, 12 a, 45, 51) having a suction inlet (11, 11 a, 50)opening fore to water, an impeller casing (10, 10 a, 43, 49) having animpeller (17, 34, 55) inscribed thereto, and a rear casing (14, 14 a,46, 53) having a delivery outlet (13, 13 a, 52) opening aft to water;and the impeller (17, 34, 55) inscribed to the impeller casing (10, 10a, 43, 49) is forward and reverse rotatable.
 2. A propulsion system forboats according to claim 1, wherein the impeller inscribed to theimpeller casing (10 a) is configured as a counter-rotating doubleimpeller (34) comprising a front impeller (34 a) and a rear impeller (34b).
 3. A propulsion system for boats according to claim 1 or 2, whereinthe impeller (14, 14 a, 46, 53) inscribed to the impeller casing (10, 10a, 43, 49) comprises axial flow blades.
 4. A propulsion system for boatsaccording to any one of claims 1 to 3, wherein the impeller casing (10,10 a, 43, 49) and the front casing (12, 12 a, 45, 51) and the rearcasing (14, 14 a, 46, 53) connected to front and rear ends of theimpeller casing (10, 10 a, 43, 49) have flow paths thereof substantiallyidentical in size of inside diameter.
 5. A propulsion system for boatsaccording to any one of claims 1 to 4, wherein: the impeller casing (10,10 a, 43) is configured arcuate; and a drive shaft (9, 35, 36) with theimpeller (17, 34 a, 34 b) fixed thereon is supported by bearings (15, 15a, 16, 16 a) disposed on front and rear peripheral walls of the impellercasing (10, 10 a, 43).
 6. A propulsion system for boats according to anyone of claims 1 to 4, wherein: the impeller casing (49) is configuredcylindrical; and a drive shaft (56) with axial flow blades (55) fixedthereon is supported by a bearing support (49) connected to a rear endof the impeller casing (49) and a bearing (57) on a side wall of thefront casing (49).
 7. A propulsion system for boats according to any oneof claims 1 to 6, wherein the suction inlet (11, 11 a, 50) of the frontcasing (12, 12 a, 45, 51) and the delivery outlet (13, 13 a, 52) of therear casing (14, 14 a, 46, 53) have plural rectification vanes (21, 22,58, 59), respectively, for rectifying water streams to inflow thepropelling machine (2, 2 a, 48) and preventing foreign matters frominflowing.
 8. A propulsion system for boats according to any one ofclaims 1 to 7, wherein: the front casing (12 a, 51) has a suction flowpath (A, A′) inclined fore; and the rear casing (14 a, 53) has adelivery flow path (B, B′) inclined aft.
 9. A propulsion system forboats according to any one of claims 1 to 8, wherein: the front casing(12, 12 a, 45, 51) and the rear casing (14, 14 a, 46, 53) of thepropelling machine are connected at lower ends thereof to fixing flanges(23, 23 a, 47, 60); and the fixing flanges (2, 23 a, 47, 60) aredetachably attached to openings of the bottom (1 b) of boat.
 10. Apropulsion system for boats according to claim 4, wherein the impellercasing (10, 10 a) is separable fore and aft.
 11. A propulsion system forboats according to claim 4, wherein: the impeller casing is separableinto an upper half of impeller casing (43 a) and a rear half of impellercasing (43 b); and the drive shaft (9 a) is supported by the upper halfof impeller casing (43 a).
 12. A propulsion system for boats accordingto any one of claims 1 to 11, wherein an inspection hole (42) isprovided to the impeller casing (10, 10 a) in a vicinity of the impeller(17, 34).
 13. A propulsion system for boats according to any one ofclaims 1 to 12, wherein a boat-side fronting branch path (64, 65) isbranched from the rear casing (63), and cooperative with the rear casingto effect a flow path selection therebetween.